Optical interferometry between image-bearing beams and their redirected phase conjugates.

Optical interferometers are commonly used for a variety of applications, including spectral analysis, displacement measurements, and gyroscopes. They were also proposed, in a more limited sense, for applications involving image processing.' In what follows we describe three new interferometers that implement mathematical operations on images borne by coherent input laser beams. Each interferometer executes a different operator of interest in image processing. The first interferometer implements the twodimensional Hartley transform of a function f(x, y, z). The Hartley transform2 is defined by